Microstructural Analysis of Carious Lesion Progression Beneath Hall Technique and Conventional Stainless‐Steel Crowns in Children

ABSTRACT

Background

Stainless‐steel crowns (SSC) are a common restorative option for preserving tooth tissue damaged by caries in primary molars. The Hall Technique (HT) is an SSC restorative approach using no local anaesthesia, tooth preparation or caries removal.

Aim

To compare carious lesion progression, biomechanical and chemical properties in exfoliated primary molars treated with HT and conventional SSC.

Design

A descriptive laboratory study was conducted with teeth treated with HT SSC and conventional SSC (control).

Results

Radiographic lesion progression was observed in half of the samples, occurring in 47% of HT SSCs and 55% of conventional SSC. The concentration of P and Ca or minor elements such as Na and Mg was similar between HT SSC and conventional SSC. Hardness values of enamel, dentine and carious lesion were slightly lower for HT SSC than conventional SSCs. Elastic modulus values for enamel and dentine were slightly higher in conventional SSC, while HT SSC had higher elastic modulus for the lesion.

Conclusion

Teeth treated with HT SSCs and conventional SSCs demonstrated similar lesion progression, elemental composition and mechanical properties, suggesting no clear differences between the treatment approaches within the limitations of the sample size and design of this study.

Why This Paper Is Important to Paediatric Dentists

1. Understand carious lesion progression in teeth with HT and Conventional SSC at the microstructural level.

2. That caries progressed beneath both in HT and conventional SSC and that fit of the SSC should be further considered in future research to understand lesion progression.

3. Suggests no major differences in the microstructure and integrity of tissues in teeth treated using either HT or conventional SSCs and should adopt the clinical approach that is best for the patient in terms of cost and acceptability.

1. Introduction

Early childhood caries affects almost half of all preschool children globally [1] and is one of the most prevalent public health issues affecting children, particularly those from low socioeconomic backgrounds [2]. Managing the disease is difficult, inefficient and expensive [3] and involves different non‐restorative or restorative options. Non‐restorative options such as sealants, fluoride varnish and silver‐diamine fluoride are often used for caries prevention or in conjunction with restorative treatment options. These approaches have shown to be effective in arresting or reversing carious lesions [4]. On the other hand, restorative options generally involve removing the carious tissues and restoring the cavity with a material such as composite, amalgam or glass ionomer cement or placing a preformed stainless‐steel crown (SSC) onto the tooth [4]. SSCs are a common restorative option for preserving the remaining tooth tissue damaged by carious lesions and have shown significant clinical success [5]. They are considered a favourable restoration for two‐surface and larger carious lesions on primary molars and a good option because of their durability, cost‐effectiveness and ease of use for some children [6, 7, 8, 9].

Any decision to restore teeth is complex and based on several factors including prognosis, caries risk and activity assessment, clinical or radiographic signs of cavitation, patient coping behaviour and patient and caregiver preferences [10, 11]. To date, there are various carious tissue removal approaches, with a recent guideline suggesting that when primary teeth require restoration, the only difference between moderate and advanced caries lesion management is that complete tissue removal is not recommended for advanced lesions due to greater risk of clinical failures. Choice of restoration material is similar for lesion depth, except the use of SSC is recommended if no carious tissue removal occurred. In all cases, the true effect is likely to be substantially different from the estimate of the effect (very low certainty of evidence), which has resulted in a clinical recommendation that recognises different choices will be appropriate for individual patients [4].

The Hall Technique (HT) is a restorative approach for the treatment of carious lesions in primary molars involving the use of SSC. The procedure involves no local anaesthesia, tooth preparation or carious lesion removal [12, 13]. The clinical effectiveness of HT has been shown in both primary and secondary care [5, 6, 14, 15, 16, 17, 18], with HT SSC teeth more likely to experience success (no retreatment, no abscess) than those treated with conventional restorations [5]. Systematic reviews on the use of SSC (including the HT) showed the validity of the HT SSC usage in primary molar teeth [8, 19, 20, 21] and a high level of acceptance of HT SSC by children and their parents [22].

There are a few differences in the management of carious primary teeth between the HT and other approaches, which might be reflected in clinical outcomes and chemical/biomechanical properties of the underlying dental tissues. A meta‐analysis showed that HT SSC had an 80% higher success rate compared to conventional restorations and showed a similar success in comparison to conventional SSC [20]. An in vitro study on microleakage in primary teeth with SSCs found more microleakage in HT SSC compared to conventional SSC, regardless of the cement used [23]. A 2021 study investigated a small sample of primary molars treated using HT and reported no radiographic change associated with lesion progression in most specimens studied. However, the results showed decreased biomechanical and chemical properties in teeth treated with the HT compared to controls [3].

Although it has been shown that sealing carious primary molars with SSCs comes with a low certainty of evidence, clinical guidelines do prioritise SSCs as a restorative option and no carious tissue removal is also recommended [4]. To further understand the effectiveness of these restorative techniques and clinical outcomes, a better knowledge of what is occurring with the tissues at the ultrastructural, biomechanical and chemical level is required. To date, there is one published study on the mechanical and chemical properties of primary teeth treated with HT prior to exfoliation [3]. The current study aimed to compare carious lesion progression, biomechanical and chemical properties in exfoliated primary molars treated using the HT and conventional SSC (controls) via radiographic imaging, elemental composition and mechanical characteristics.

2. Materials and Methods

2.1. Study Sample

The samples used in this study were collected from a primary care randomised clinical trial, examining the clinical performance of the Hall Technique in children [5]. These samples were collected opportunistically, as the collection of teeth was not part of the original aims of the clinical trial. The original study and the subsequent laboratory study of collected teeth had ethical approval from the Central Health and Disability Ethics Committee of New Zealand (14/NTB/39). The original study examined outcomes of SSCs placed in children; participants received either HT or conventional restorations with GIC, composite, amalgam or a conventional SSC. Informed consent was received by the parent/caregiver. For this cross‐sectional observational and descriptive study, the sample consisted of teeth retrieved from children treated with a HT SSC and conventional SSC (control). Inclusion criteria for the children who received the HT and conventional SSC are outlined in the randomised clinical trial [5]. For the HT, the preformed, pre‐crimped 3M ESPE SSCs were placed without local anaesthetics or carious tissues removal. Crowns were cemented with 3M RelyX Luting Plus RMGI Cement. For the conventional SSC, infected enamel and dentine were removed with high and slow speed drills, usually under local anaesthetic. The occlusal, mesial and distal surfaces were reduced, and the SSC was cemented with Fuji I GC Cement. Recovered specimens were collected 2–3 years post‐treatment when the teeth exfoliated; none of those received endodontic treatment after SSC placement. Thirty‐nine teeth were collected; 22 teeth were treated by HT SSC, and 17 teeth were treated by conventional SSC. The following lab analyses follows the protocol of an earlier pilot study of 16 teeth that examined the ultrastructure and properties of HT‐treated teeth [3].

2.2. Specimen Preparation

Samples (treated molar teeth) were preserved dry after exfoliation. Samples were dehydrated using ascending concentrations of ethanol, cleared with xylol and embedded in Methyl‐methacrylate resin in glass containers. After setting, embedded blocks were removed from the glass containers and cut into sections using a Struers Accutom‐50 precision cut‐off saw (Struers, Copenhagen, Denmark) with a R330 diamond wafered wheel under water irrigation. Teeth were sectioned in the mesio‐distal plane, and one to three 800 μm thick central sections were generated for each specimen. The most central section or the one that provided the best representation of the carious lesion was chosen for further laboratory analysis. In conventional SSC specimens (which underwent caries removal), subsequent tests were carried out in the remaining hard tissues adjacent to the caries lesion. Sections were mounted on plastic slides and polished in a Struers TegraPol‐21 polisher (Struers, Copenhagen, Denmark) at 180 rpm. The polishing was carried out under water irrigation using Silicon Carbide papers of coarse to finer grit size (P#1200, P#2400 and P#4000) until a thickness of 100–200 μm was obtained. To ensure accuracy, a digimatic indicator was used to measure section thickness.

2.3. Radiographic Imaging and Analysis

Diagnosis of the baseline lesion category and depth were obtained by the trained and calibrated treatment providers who read all radiographs, with intraclass correlation coefficient for the inter‐examiner reliability score 0.85, and the intra‐examiner scores were 0.86 and 0.88 [5]. Pre‐treatment bitewing radiographs were scored for lesion depth using the P‐scoring system (for review) [24]. Post‐treatment radiographs were obtained from central sections of exfoliated teeth obtained for lab analyses. Conventional post‐treatment radiographs are not practical due to the superimposition of the SSC, which obscures carious lesions. Post‐treatment radiographs of sectioned teeth were taken using a digital portable dental X‐ray machine (Arribex Nomad Pro 2 portable X‐ray machine with 0.12 s exposure, 60 kV and 2.5 mA, focus film distance of 20 cm). Post‐treatment scoring was performed by two trained and calibrated examiners (paediatric dental specialist and final year dental student) also based on the P‐scoring system [24]. Radiographic scoring of the pre‐ and post‐treatment radiographs was performed blinded to the treatment provided. Scoring between examiners was compared, and consensus was achieved in cases of discrepancy by re‐examining films together and subsequent discussion, as described in the earlier RCT trial examining the clinical performance of the HT in children [5]. Carious lesion progression was assessed by comparing pre‐ and post‐treatment radiographic scores to provide a radiometric estimate of caries progression (Table 1).

TABLE 1.

Specimens analysed for radiographic caries progression.

Specimen ID	Tooth number	SSC treatment method	Baseline lesion depth	Follow‐up lesion depth	Lesion change
1305	65	HT	P4	P5	+1
1126	75	HT	P4	P5	+1
1183	84	HT	P3	P4	+1
1202	54	HT	P4	P5	+1
1257	54	HT	P3	P4	+1
1478	75	HT	P4	P5	+1
1120	54	HT	P3	P4	+1
1354	75	HT	P3	P3	0
1582	74	HT	P4	P4	0
1355	85	HT	P4	P4	0
1426	74	HT	P4	P4	0
1306	54	HT	P4	P4	0
1013‐2	65	HT	P4	P3	−1
1354	65	HT	P3	P0	−3
1371	74	HT	P4	P0	−4
1150	54	Conventional	P4	P5	+1
1264	54	Conventional	P3	P4	+1
1105	64	Conventional	P4	P5	+1
1706	54	Conventional	P4	P5	+1
1740	64	Conventional	P3	P4	+1
1428	65	Conventional	P4	P4	0
1423	64	Conventional	P4	P4	0
13 572	84	Conventional	P3	P0	−3
1425	54	Conventional	P4	P0	−4

2.4. Elemental Analysis

Following carbon coating, elemental composition analysis was conducted using Energy‐Dispersive X‐ray (EDX) spectroscopy using a Zeiss Sigma VP FEG‐SEM housed at Otago Micro and Nanoscale Imaging (OMNI, University of Otago). EDX analysis was performed at 20 kV accelerating voltage, 60 μm aperture size and 8.5 mm working distance. Elemental mapping was used to visualise and assess the concentrations of major elements such as calcium (Ca) and phosphorus (P), as well as minor elements including sodium (Na), magnesium (Mg), chlorine (Cl), fluorine (F) and strontium (Sr) in targeted regions. EDX mapping was conducted for 10 min per sample. Chemical composition data were processed using Aztec software (Oxford Instruments Nano‐Analysis).

2.5. Mechanical Properties Analysis

A subset of representative samples of each group was selected for mechanical properties testing, due to the time‐consuming and labour‐intensive preparation required. These samples were considered most suitable for analysis because they exhibited clearly defined regions of sound enamel and dentine, while the carious lesion was confined to a separate surface from the areas selected for sound tissue analysis. Samples were screened for structural integrity and absence of preparation or sectioning artefacts such as cracks, voids or excessive material loss. The selected slides were repolished on the Struers TegraPol‐21 polisher with SiC paper (1200 grit) and finished with 1 μm diamond paste. Each sample was checked on a microscope for polishing quality (absence of scratches and defects). Samples were then cleaned with 90% ethanol for 3 min in an ultrasonic bath. Polished slides were mounted on magnetic bases using mounting wax and placed into a paralleling machine (Leitz, Wetzlar, Germany). Tests were carried out in a nanoindenter (Ultra Micro‐Indentation System, UMIS‐2000, CSIRO, Australia). The attached video‐microscope was used to determine the indenting positions for the different dental tissues. An array size of 6 × 6 indents with 40 μm spacing was performed in sound enamel and dentine on the opposite side of the carious lesion. A similar array was also performed in the carious area. Each test ran for around 2 h in standard laboratory conditions. A loading force of 50 mN was applied using a three‐sided pyramidal Berkovich tip (Synton, Switzerland). Calculation of hardness (H) and elastic modulus (E) values was done using the UMIS software. Mean and standard deviation values of hardness and elastic modulus for dentine, enamel and carious lesion were then obtained for each sample.

2.6. Statistical Analysis

Descriptive statistics were used to summarise carious lesion progression, biomechanical properties and chemical composition of exfoliated primary molars treated with the HT and conventional SSC. Continuous variables were reported as means and standard deviations (SD), while categorical variables were presented as frequencies and percentages.

3. Results

Exfoliated teeth were recovered from 39 children who were 4–7 years of age when the crowns were placed, with slightly more teeth recovered from females (n = 17) than males (n = 16). There were 22 HT SSC and 17 conventional SSC. Of the 39 teeth, 24 had pre‐treatment radiographs available for analysis, with two‐thirds of the sample being primary first molars (66.7%, n = 16), as shown in Table 1.

Of the 24 specimens analysed for carious lesion progression, two‐thirds of the SSC‐treated teeth had lesions into the middle third of dentine (P4) with a similar distribution between the HT SSC and conventional SSC teeth. Half of the samples showed signs of lesion progression with less than a third experiencing no change and one‐fifth showing improvement. Lesion progression occurred in both HT SSCs and conventional SSC in 47% and 55% of the samples, respectively (Figure 1, Table 1).

FIGURE 1.

Radiographic assessment of lesion progression. Pre (a) and post‐op (b) radiographs of specimen #1120 tooth 54 treated with the Hall Technique. Pre (c) and post‐op (d) radiographs of specimen #1150 tooth 54 treated with Conventional SSC.

3.1. Elemental Analysis

Elemental analysis was conducted to determine the oxide wt% of major and minor elements in the dental tissues (Table 2, Figure 2). The concentration of most elements such as Ca, P and Na was higher in sound enamel compared to other regions, whereas Mg was higher in sound dentine. The results showed similar concentration of P and Ca between HT SSC (n = 22) and conventional SSC (n = 17) samples, although a slightly higher concentration of P and Ca was observed in the enamel lesion area of conventional SSC samples. The concentration of minor elements such as Na and Mg was also similar between HT SSC and conventional SSC teeth. Conversely, Sr. concentration was higher in conventional SSC teeth, except for sound dentine where HT‐treated teeth had higher levels. Cl was not detected in both HT SSC and conventional SSC teeth. Overall, although minor variations were detected, the elemental composition between HT SSC and conventional SSC teeth was relatively similar.

TABLE 2.

Oxide %wt (±SD) in sound enamel, dentine and carious lesion enamel and dentine areas in HT SSC and conventional SSC teeth samples.

Element	Area	HT SSC	Conventional SSC
Calcium (Ca)	Sound enamel	48.98 (0.84)	49.06 (0.84)
	Sound dentine	33.82 (0.90)	34.27 (1.18)
	Lesion enamel	42.37 (5.90)	47.30 (3.01)
	Lesion dentine	26.43 (5.50)	26.53 (10.61)
Phosphorous (P)	Sound enamel	39.40 (0.8)	39.47 (0.73)
	Sound dentine	27.98 (0.9)	28.25 (1.11)
	Lesion enamel	34.69 (4.11)	38.41 (2.48)
	Lesion dentine	22.64 (4.97)	22.13 (8.40)
Sodium (Na)	Sound enamel	1.14 (0.09)	1.15 (0.11)
	Sound dentine	0.75 (0.11)	0.78 (0.09)
	Lesion enamel	1.04 (0.78)	0.88 (0.13)
	Lesion dentine	0.51 (0.21)	0.59 (0.31)
Magnesium (Mg)	Sound enamel	0.47 (0.08)	0.49 (0.10)
	Sound dentine	1.27 (0.18)	1.26 (0.83)
	Lesion enamel	0.42 (0.17)	0.58 (0.40)
	Lesion dentine	0.55 (0.34)	0.71 (0.45)
Strontium (Sr)	Sound enamel	−0.02 (0.06)	−0.01 (0.07)
	Sound dentine	0.33 (0.04)	0.01 (0.08)
	Lesion enamel	0.38 (0.33)	0.56 (0.70)
	Lesion dentine	1.12 (1.09)	0.81 (0.70)

FIGURE 2.

Example of areas selected for elemental mapping for specimen #1582. (a) Sound tissues. (b) Carious lesion area. De = Dentine; En = enamel.

3.2. Mechanical Properties

Twelve representative teeth (visible carious lesion; presence of sound enamel away from the lesion area) were analysed for measurement of hardness and elastic modulus; 6 HT SSC and 6 conventional SSC. The average hardness of sound enamel was 4.77 GPa (∓ 0.64) for teeth treated with HT SSC (Figure 3). This value was slightly lower than the hardness of enamel treated with conventional SSCs, which averaged 4.91 GPa (∓ 0.42). Similarly, hardness values for dentine for HT SSC teeth were slightly lower at 0.98 GPa (∓ 0.15), compared to 1.05 GPa (∓ 0.13) for conventional SSC. Hardness values for the carious lesion area were lower in HT SSC (average of 0.38 GPa (∓ 0.10)), while conventional SSCs had a slightly higher hardness average of 0.42 GPa (∓ 0.27). The hardness values of enamel, dentine and lesion were all slightly lower for HT SSC than conventional SSCs.

FIGURE 3.

Mechanical properties in sound dentine, enamel and carious lesion area in Hall and Conventional teeth. (a) Hardness. (b) Elastic modulus.

The average elastic modulus value of sound enamel was 90.09 GPa (∓7.08) for teeth treated with HT SSC (Figure 3). This value was slightly lower than the elastic modulus value of enamel treated with conventional SSC, which averaged 91.98 GPa (∓4.37). Elastic modulus values for dentine for HT SSC teeth were slightly lower with an average value of 23.53 GPa (∓2.91), compared to 24.39 GPa (∓2.31) for conventional SSC. Elastic modulus values for the carious lesion area were slightly lower in conventional SSC (average of 9.36 GPa (∓5.80), while HT SSC had an average of 9.46 GPa (∓2.35)). Teeth treated with conventional SSC had slightly higher elastic modulus values for both enamel and dentine compared to specimens treated with HT SSC. Teeth treated with HT SSC also had slightly higher elastic modulus values for the lesion area than conventional teeth.

4. Discussion

This study investigated carious lesion progression, elemental composition and mechanical properties in exfoliated primary molars treated using the HT SSC and conventional SSC. The overall goal was to enhance our understanding of lesion progression to help with management decisions in paediatric dentistry when using SSC for managing dental caries. We observed radiographic lesion progression in approximately half of the samples. Elemental analysis also showed similar concentrations of P and Ca and minor elements such as Na and Mg between HT SSC and conventional SSC. In the representative specimens chosen to analyse mechanical properties, there were small differences in hardness and elastic modulus values between HT SSC and conventional SSC but likely not significant.

This study has some limitations with the specimens being heterogeneous regarding technique preparation methods, tooth types, baseline carious lesion depth, different cements used and varied retrieval times. As the study primarily centred on comparing the material/laboratory performance of HT SSC and conventional SSC teeth, patients' individual factors and the key cofounding factors mentioned above could have impacted the outcomes of these techniques, introducing variability into the results. Nevertheless, this study offers valuable data for enhancing our understanding of the biological mechanisms underlying carious lesions progression in teeth treated with SSCs regardless of the approach. This is the second study of its kind investigating microstructural analysis of carious lesion development beneath SSCs and potential mechanisms that underline the clinical outcomes of the techniques. This study has strengths that build on the previous pilot study (see Loch, Jansen van Vuuren [3]), due to the larger number of specimens collected and analysed; however, a cautious approach when interpreting these findings is needed due to the limited sample sizes and limitations mentioned above.

Previous studies including systematic reviews show HT SSC to be more successful clinically compared to other restorative materials [5, 17, 19, 20, 25, 26, 27]. While there is a substantial body of literature on the clinical performance of the HT SSC, research on the underlying biological mechanisms and progression of carious lesions remains scarce. Radiographic assessment of primary molars prior to SSC treatment is advisable to assess for carious lesion depth, and pulp‐dentine complex health, which may affect the suitability of SSCs for caries management [9, 28]. In this context, post‐treatment radiographs are recommended to assess treatment success, but although clinical radiographs can be a feasible tool to assess crown margin adaptation and pulpal pathology in SSC‐treated teeth, carious lesion progression cannot be assessed as SSCs obscure the coronal structure of the tooth [29]. Thus, in this study we conducted radiographic assessment of sectioned teeth post‐exfoliation as outlined in our earlier study to assess caries progression [3]. It is important to acknowledge that the use of two different imaging modalities—traditional bitewing radiographs at baseline and radiographs of sectioned teeth post‐treatment—may limit direct comparability and introduce some degree of measurement inconsistency. Despite these limitations, this approach currently represents the most viable option, as conventional bitewing radiography cannot reveal internal details on SSC specimens.

This study highlights that there seemed to be small differences in lesion progression (47% and 55%) and reduction (20% and 22%) between HT SSCs and conventional SSCs, respectively. This differs from our earlier study where only two of the 11 (19%) HT SSC teeth showed lesion progression [3]. This earlier work was thought to provide evidence that caries did not progress over most of the specimens, with lesion progression happening under the HT SSC. Due to the significant clinical success of SSCs over many decades, it has been suggested that a well‐fitted SSC will stop or slow down caries progression [11]. With a slightly larger sample of teeth in the current study, it seems that caries progressed in half of the teeth regardless of technique used. In these specimens, progression was slightly more evident in the conventional SSC. However, the clinical success of these teeth did not differ, even with caries progressing in half the teeth, as all teeth exfoliated naturally and were not considered major failures (i.e., irreversible pulpitis, dental abscess, inter‐radicular radiolucency and crown loss with unrestorable tooth). Previous studies have shown that the HT SSC performs similarly to the conventional SSC clinically [5, 9, 17, 25, 30], and now, we have further evidence that HT SSCs may share similar caries progression rates as conventional SSCs.

There appears to be no implications in the current study from lesion progression as all teeth exfoliated naturally. However, this may be important depending on the time taken for primary molar teeth to exfoliate and whether caries progression leads to a major failure. It is still unclear in the literature if residual infected dentine or dental biofilm is the primary driver of lesion progression, particularly in deep cavitated lesions [31, 32]. The premise of the HT is based on preventing biofilm formation and arresting caries by isolating the infected dentine from the oral cavity. In this study, conventional SSC teeth were managed with local anaesthetic administered as required, rotary and hand instruments used to excavate the carious dental tissue with a selective caries removal approach to avoid pulp exposure [5]. The remaining caries not removed may have also led to caries progression, like what happens in the HT. A recent study has shown that both the HT and modified HT (where the necrotic and contaminated outermost layer of the carious lesion was removed with an excavator) exhibited high success rates over a 24‐month follow‐up period, with no differences observed between the two methods [33]. However, radiographic progression was not examined in this study. Crown fit was identified and showed that both the HT and modified HT groups exhibited similar numbers of SSCs with insufficient fit, but their clinical outcomes differed. There was a significant difference with major failures in teeth with insufficient SSC fit in the HT group [33]. This may suggest that marginal leakage can cause any residual carious tissue to reactivate and progress, and this may depend on the amount of caries left behind. In the current study, crown fit of both the HT and conventional SSC was not examined and could have been a reason for half of the carious lesions progressing; however, such progression was not enough to cause major failure.

Mechanical property values are related to the mineral content of calcified tissues [34, 35], with a reduction of the mineral content linked to a decrease in mechanical properties of carious dentine [36, 37]. In this study, higher concentrations of calcium and phosphorous were found in sound enamel, followed by dentine and then the carious lesion. In this study, the average oxide %wt values for HT SSC and conventional SSC teeth were similar and within previously reported values [38, 39, 40]. Other studies have reported lower values in sound enamel and carious lesions [41, 42]. Differences between studies are likely due to instruments and analytical settings used; however, both studies [41, 42] have shown reduction in calcium and phosphorus concentration in carious enamel when compared to sound enamel [42]. The lower calcium and phosphorous levels observed in the carious lesions further corroborate the lower mechanical values estimated for these areas in this study. Of note is that the oxide %wt of calcium and phosphorus was similar between HT SSC and conventional SSC.

This study suggests that teeth treated with both HT SSC and conventional SSC showed overall similar lesion progression/reduction (assessed via radiographic imaging), elemental composition and mechanical properties of dental tissues. This suggests similar microstructure and integrity of tissues in teeth treated using either approach and provides further support that the HT should be part of an evidence‐based management tool for managing deep carious lesions in primary molars. The fit of the SSC should be further considered in future research to understand lesion progression under the HT, modified HT and conventional SSCs. From this perspective, clinicians should adopt the clinical approach that is best for the patient in terms of cost and acceptability.

Author Contributions

Conceived the ideas – C.L., L.A.F.P. and D.H.B. Collected the data – C.L. and D.H.B. Analysis of the data – C.L., P.R., I.A.‐M., S.A., M.A.‐S. and M.A.‐A. Led the writing of the paper – C.L. and L.A.F.P. Edited paper – C.L., D.H.B., L.A.F.P., P.R., I.A.‐M., S.A., M.A.‐S. and M.A.‐A.

Funding

This work was supported by Cure Kids. Sir John Walsh Research Institute, University of Otago.

Ethics Statement

Ethics approval from the Central Health and Disability Ethics Committee of New Zealand (14/NTB/39).

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

Data S1: ipd70104‐sup‐0001‐Supinfo.docx.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.